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0 pointscompsciphd1y ago0 comments

they did it "simpler", i.e. academic work has to be "perfect" in a way a product does not. so (from my perspective), they punted the entire concept of making what I would refer to as a "layer aware linux distribution" and just created layers "on demand" (via RUN syntax of dockerfiles).

From an academic perspective, its "terrible", so much duplicate layers out in the world, from a practical perspective of delivering a product, it makes a lot of sense.

It's also simpler from the fact that I was trying to make it work for both what I call "persistent" containers (ala pets in the terminology) that could be upgraded in place and "ephemeral" containers (ala cattle) when in practice the work to enable upgrading in place (replacing layers on demand) to upgrade "persistent" containers I'm not sure is that useful (its technologically interesting, but that's different than useful).

My argument for this was that this actually improves runtime upgrading of systems. With dpkg/rpm, if you upgrade libc, your systems is actually temporarily in a state where it can't run any applications (in the delta of time when the old libc .so is deleted and the new one is created in its place, or completely overwrites it), any program that attempts to run in that (very) short period time, will fail (due to libc not really existing). By having a mechanism where layers could be swapped in essentially an atomic manner, no delete / overwrite of files occurs and therefore there is zero time when programs won't run.

In practice, the fact that a real world product came out with a very similar design/implementation makes me feel validated (i.e. a lot of phd work is one offs, never to see the light of day after the papers for it are published).

0 comments

pxc1y ago

> so (from my perspective), they punted the entire concept of making what I would refer to as a "layer aware linux distribution"

Would you consider there to be any 'layer-aware Linux distributions' today, e.g., NixOS, GuixSD, rpm-ostree-based distros like Fedora CoreOS, or distri?

> so much duplicate layers out in the world

Have you seen this, which lets existing container systems understand a Linux package manager's packages as individual layers?

https://github.com/pdtpartners/nix-snapshotter

mananaysiempre1y ago

(Not GP.)

NixOS can share its Nix store with child (systemd-nspawn) containers. That is, if you go all in, package everything using Nix, and then carefully ensure you don’t have differing (transitive build- or run-time) dependency versions anywhere, those dependencies will be shared to the maximum extent possible. The amount of sharing you actually get matches the effort you put into making your containers use the same dependency versions. No “layers”, but still close what you’re getting at, I think.

On the other hand, Nixpkgs (which NixOS is built on top of) doesn’t really follow a discipline of minimizing package sizes to the extent that, say, Alpine does. You fairly often find documentation and development components living together with the runtime ones, especially for less popular software. (The watchword here is “closure size”, as in the size of a package and all of its transitive runtime dependencies.)

pxc1y ago

> On the other hand, Nixpkgs (which NixOS is built on top of) doesn’t really follow a discipline of minimizing package sizes to the extent that, say, Alpine does. You fairly often find documentation and development components living together with the runtime ones, especially for less popular software. (The watchword here is “closure size”, as in the size of a package and all of its transitive runtime dependencies.)

Yep. I remember before Nix even had multi-output derivations! I once broke some packages trying to reduce closure sizes when that feature got added, too. :(

Besides continuing to split off more dev and doc outputs, it'd be cool if somehow Nixpkgs had a `pkgsForAnts` just like it has a `pkgsStatic`, where packages just disable more features and integrations. On the other hand, by the time you're really optimizing your Nix container builds it's probably well worth it to use overrides and build from source anyway, binary cache be damned.

compsciphdOP1y ago

I'll try to get back to this to give a proper response, but can't promise.

j / k navigate · click thread line to collapse

0 pointscompsciphd1y ago0 comments

From an academic perspective, its "terrible", so much duplicate layers out in the world, from a practical perspective of delivering a product, it makes a lot of sense.

0 comments

pxc1y ago

> so (from my perspective), they punted the entire concept of making what I would refer to as a "layer aware linux distribution"

Would you consider there to be any 'layer-aware Linux distributions' today, e.g., NixOS, GuixSD, rpm-ostree-based distros like Fedora CoreOS, or distri?

> so much duplicate layers out in the world

Have you seen this, which lets existing container systems understand a Linux package manager's packages as individual layers?

https://github.com/pdtpartners/nix-snapshotter

mananaysiempre1y ago

(Not GP.)

pxc1y ago

Yep. I remember before Nix even had multi-output derivations! I once broke some packages trying to reduce closure sizes when that feature got added, too. :(

compsciphdOP1y ago

I'll try to get back to this to give a proper response, but can't promise.

j / k navigate · click thread line to collapse